parse: Account for EOF when checking for whitespace ...

When parsing a file that doesn't end with whitespace (like a new line),
the parser would choke on having no symbols left. Fix that.

Fixes: 1519cef

parse: Decode file as UTF-8 ...

I was testing the parser with binary input.
Use Unicode instead and make sure we pass it that.

Add test harness and simple fuzz test

make: Add way to build NewLang executable

src: Reformat using black

Restructure files